Antennas are used in communication systems to send and receive information using electromagnetic waves. Systems that use antennas include short-range communication links for wireless networks, such as Wireless Fidelity (WiFi), cellular phone, or Bluetooth, for example. Some antenna systems are designed primarily for receiving broadcast signals transmitted from great distances, such as cellular towers or communication satellites, for example. In some applications, the functionality provided by a quality antenna system may be incorporated into devices such as laptop computers, positioning systems, handheld computing devices, industrial controllers, local area networks (LANs), and many other devices.
As devices are reduced in physical size, antenna systems are needed that are compact enough to be integrated into smaller and smaller devices. Some types of antenna designs are more suitable for integration into the housings of common electronic devices, such as laptops or computer peripheral devices. One type of antenna suitable for some of these applications is a patch antenna.
A patch antenna may be implemented, for example, as one or more conductive areas, or patches, on a printed circuit board. Patches may have any suitable geometric shape, including rectangles, circles, triangles, or bow ties. Multiple patches may be laid out in an array. The geometric shape and layout of the patches determine how the antenna will perform in terms of beam pattern and beam width. Generally speaking, a multi-element patch antenna will have a narrower beam width than a single element patch antenna.
For a given multi-element patch antenna, the performance of the antenna when coupled to receive or transmit circuitry depends on the patch antenna's bandwidth. The bandwidth of an antenna is a measure of its ability to operate over a specified range of frequencies. Unlike some antenna properties, bandwidth does not have a universally accepted and unique definition, in part because the bandwidth may depend on operational requirements of the antenna. However, a wide bandwidth antenna generally has good performance over a wider range of frequencies than a narrow bandwidth antenna. Bandwidth may be affected by factors such as input impedance, signal loss, antenna pattern, and standing wave ratio (SWR) on the antenna's feed network. A feed network for a patch antenna provides an electrically conductive path between transmit or receive circuitry and the elements of the patch antenna.
Accordingly, the feed network that couples the elements of the antenna to the transmit or receive circuitry plays a significant role in determining the effective bandwidth of the antenna in the overall system. As such, an important element in the design of a multi-element patch antenna system is the design of the feed network.